|Byrne, Frank - UC, RIVERSIDE, CA|
|Prabhaker, Nilima - UC, RIVERSIDE, CA|
|Toscano, Nick - UC, RIVERSIDE, CA|
Submitted to: Pesticide Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 18, 2002
Publication Date: March 1, 2003
Citation: Byrne, F.J., Castle, S.J., Prabhaker, N., Toscano, N.C. 2003. Biochemical study of resistance to imidacloprid in b-biotype bemisia tabaci from guatemala. Pesticide Management Science 59: 347-352. Interpretive Summary: A population of Bemisia tabaci originating from cantaloupe fields in Guatemala demonstrated high levels of resistance to the systemic insecticide imidacloprid in a series of systemic uptake bioassays. This is the first example of resistance to imidacloprid in B. tabaci occurring in an outdoor agricultural setting in contrast to earlier examples from protected agriculture or artificial selection applied to a captured population. The practice of growing serial plantings of cantaloupes in Guatemala over a 9 month period likely contributed to high selection pressure for resistance to imidacloprid. Biochemical evaluation of this population failed to reveal the role of mixed function oxidases in conferring resistance to imidacloprid in B. tabaci.
Technical Abstract: Systemic uptake bioassays using excised cotton leaves confirmed resistance to imidacloprid in a Guatemalan population of the tobacco whitefly Bemisia tabaci Gennadius. Polyacrylamide gel electrophoresis of naphthyl esterases identified the insects as B-types. Upon collection from the field, resistance was determined to be 58-fold relative to a susceptible strain originating in the Imperial Valley of California. Resistance levels increased to 126-fold in this population during its continuous exposure to systemically treated cotton. In biochemical investigations, there was no detectable NADPH-dependent mixed function oxidase metabolism of 14C-imidacloprid at any time during the selection process. In contrast, microsomal preparations from housefly abdomens readily produced significant amounts of the mono-hydroxy and olefin derivatives of the parent compound. Detoxification of imidacloprid by housefly MFOs may account for reports of lower toxicity of the insecticide towards this insect compared with whiteflies, despite similar binding properties between imidacloprid and the nicotinic acetylcholine receptors in both species.